A box contains $10$ red balls, $4$ green balls, and $3$ blue balls. If a ball is randomly chosen, what is the probability that it is not green?
Answer: There are $10 + 4 + 3 = 17$ balls in the box. There are $4$ green balls. That means $17 - 4 = 13$ are not green. The probability is $ \frac{13}{17}$.